Tissue liquefaction and aspiration

ABSTRACT

A method and apparatus are disclosed for liquefying target tissue within a body and aspirating the same while leaving non-target tissue intact. A biocompatible fluid is heated and contacted with target tissue so that the target tissue is melted while non-target tissue remains intact. As the target tissue is being melted it is also aspirated from the body.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.08/823,713 filed Mar. 25, 1997 now U.S. Pat. No. 6,074,358, which is adivision of U.S. application Ser. No. 08/384,655 filed Feb. 6, 1995, nowU.S. Pat. No. 5,616,120.

BACKGROUND OF THE INVENTION

The present invention is directed toward a method for liquefying targettissue within a body and more particularly, toward a method of heating abiocompatible fluid and presenting such to target tissue, therebyliquefying the target tissue and aspirating it while leaving non-targettissue intact.

Prior thermal energy sources used in surgery have been “dry-heat”devices. Some examples are: thermal lasers, ultrasound, microwave, radiofrequency, and electrosurgery devices. These dry-heat energy sourcestransfer heat from a surgical instrument to a tissue primarily by theheat transfer modalities of conduction and radiation. Thermal lasers,ultrasound, and microwave energy sources can liquefy tissue, but only atvery high energy levels. If any of these dry-heat energy sources areplaced in direct contact with target surgical tissue, there is no tissuedifferentiation. That is, healthy as well as unhealthy tissue will beliquefied. For example, collapsing cavitation bubbles in front of anultrasound surgical instrument release a thermal energy of 13,000° F.per bubble. With such a high thermal energy input there is nodifferentiation of tissue within the surgical tissue field. That is, alltissue target and non-target, within the target field melts orliquefies. The thermal energy in thermal lasers and ultrasound isinherently high, so the heat cannot be “turned down” or reduced. Inmicrowave, radio frequency, and electrosurgery the level of thermalenergy may be reduced but in so doing, liquefaction of tissue is notachieved at all. Rather, cauterization or coagulation of the tissueresults.

U.S. Pat. No. 4,924,863 discloses a method for removing artheroscleroticplaque from a patient by heating the plaque under pressure for a limitedperiod of time. When the plaque is heated, it liquefies without causingimmediate death of the underlying tissue. The liquefied plaque is thenaspirated from the body through a catheter. The means used for heatingthe plaque is microwave or radio frequency energy. As discussed above,however, in an effort to control the level of energy being produced, allof the plaque may not liquefy.

U.S. Pat. No. 5,540,679 discloses the use of a balloon catheter forheating tissue in a patient's body. A heating device is located withinthe balloon and is arranged for heating fluid inside the balloon. Whenthe fluid is heated, unwanted tissue, such as a tumor or an enlargedprostate gland, is heated by thermal conduction from the fluid through awall of the balloon. The heat destroys the tissue which is eventuallyabsorbed into the patient's body. This method uses conduction an& asexplained above, such a method creates such a high level of energy thatthere is no tissue differentiation. As a result, healthy tissue may beheated and ultimately destroyed.

U.S. Pat. No. 4,886,491 discloses a method of liposuction using anultrasonic probe. An ultrasonic probe tip is vibrated at a highfrequency and a low amplitude. This method separates the fatty tissueand creates heat which melts some of the fatty tissue. A salineirrigating solution is applied to the area which emulsifies the meltedfatty tissue. The emulsified solution is then aspirated. Again, becauseof the high thermal energy input into the system there is nodifferentiation of tissue into target and non-target tissue.

SUMMARY OF THE INVENTION

The present invention is designed to overcome the deficiencies of theprior art discussed above. It is an object of this invention to providea method for liquefying target tissue within a living body while leavingnon-target tissue intact, and aspirating the liquefied tissue as it isliquefied.

It is another object of the invention to provide a method for liquefyingtarget tissue by heating a biocompatible fluid and presenting the sameto the target tissue.

It is a further object of the invention to provide a method forliquefying fatty tissue and aspirating the same from a patient.

In accordance with the illustrative embodiments, demonstrating featuresand advantages of the present invention, there is provided a method forliquefying target tissue within a human body. The method includesheating a biocompatible fluid, presenting this fluid to the targettissue which liquefies the tissue, while leaving non-target tissueintact, and aspirating the liquefied tissue as soon as it is liquefied.

The present invention discloses a novel energy source which allows forefficient, safe, minimally invasive, and cost-effective surgery forsurgical procedures where the goal of the surgery is to remove unwantedtissue from the body, within a surgical tissue field. The presentinvention also allows for the differentiation of target tissue fromnon-target tissue. In other words, the surgical tissue field is definedas the actual anatomical landscape with which the surgeon is physicallyinteracting. Surgical tissue fields are comprised of multiplehomogeneous tissue groups. Each of these homogeneous tissue groups hasits own melting point. With the present invention, the melting point ofa particular tissue group or unwanted tissue is determined in order toliquefy the tissue and rid the patient of the same.

Other objects, features, and advantages of the invention will be readilyapparent from the following detailed description of a preferredembodiment thereof taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

For the purpose of illustrating the invention, there is shown in theaccompanying drawing one form which is presently preferred; it beingunderstood that the invention is not intended to be limited to theprecise arrangements and instrumentalities shown.

The sole FIGURE is an elevational view of a liquefaction and aspirationdevice of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing in detail, there is shown in the FIGURE aliquefaction and aspiration device constructed in accordance with theprinciples of the present invention and designated generally as 10.

The liquefaction device 10 includes a hollow handpiece 12 with a firstend 14 and a second end 16. An elongated cannula 18 extends from thefirst end 14 of the handpiece 12 and terminates in a tip 20. The tip 20has three ports formed therethrough. Three lumens 22, 24, and 26 arepositioned in the cannula. Each of the lumens has one end communicatingwith a corresponding port and an opposite end extending into thehandpiece 12.

An irrigation tube 28 has one end thereof connected to the lumen 24 andan opposite end connected to a fluid source 30. The fluid source isheated by a heating element (not shown) that can be located within oroutside of the handpiece 12. The heated fluid source 30 supplies heatedfluid through the heated irrigation tube 28 and out of the tip 20 of thecannula 18 via the port associated with the lumen 24. A variety ofsolutions that are compatible with the tissue being treated can beutilized. However, a preferred heated fluid is a saline solution. Thesaline solution is heated to a temperature between 98.6° F. and 250° F.This temperature defines the minimum threshold temperature of the liquidthat is required to cause liquefaction of a specific substance when theheated liquid is presented to the specific substance. The heated fluidcan be fed utilizing a pump mechanism or simply by the force of gravity.

A cooled solution irrigation tube 32 has one end thereof connected tothe lumen 26 and an opposite end connected to an irrigation supplysource 34. The irrigation supply source supplies fluid through theirrigation tube 32 and out of the tip 20 of the cannula via the portassociated with the lumen 26. Once again, the preferred irrigationsolution is a saline solution. The irrigation supply source ispreferably mounted above the handpiece 12 so that gravity continuouslyfeeds the irrigation solution through the irrigation tube 32 and out ofthe tip 20 of the cannula 18. It should be readily apparent, however,that a pump could also be used. This irrigation solution may be chilledpre-operatively or cooled intra-operatively. The preferred temperaturefor the cooled solution is believed to be approximately 40° F., althoughthe optimal temperature will vary depending on the temperature of theheated solution and the configuration of the tip 20. That is, thetemperatures of the solutions will vary depending on the type of tissuebeing liquefied. Furthermore, the tip 20 is disposable and may vary insize and shape depending upon what area of the body is being treated.

An aspiration tube 36 has one end connected to the lumen 22 and theopposite end connected to a vacuum source 37. The vacuum source 37causes the target tissue and the saline solution to be aspirated fromthe surgical tissue field through the tip 20 of the cannula via the portassociated with the lumen 24. It should be noted that all of the aboveoperations are preferably controlled through a controller circuit 38.

A cooled solution is fed through the irrigation tube 32, through thelumen 26 and out the corresponding port in the tip 20 of the cannula 18.The flow from the irrigation source 34 is controlled by the surgeon in amanner well known in the art (e.g., a foot actuated flow controlswitch).

To carry out the present method, the tip 20 of the cannula 18 isinserted into the surgical tissue field. Heated saline solution is fedthrough the tube 28, through the lumen 24, and out of the tip 20. Thesolution should be heated to the melting point of the target tissue.Upon contact with the heated solution, the target tissue rapidlyliquefies. By manipulating the temperature of the biocompatible liquid,the natural melting point of the target tissue may be taken advantage ofto achieve selective liquefaction. It is because the total thermalenergy input into the system is so low and because the thermal energy isliquid and in motion that selective liquefaction is achieved. Generally,most target surgical tissue has a lower melting point than non-targettissue because the non-target (or non-pathologic) tissue has greaterstructural integrity than target (or pathologic tissue).

The liquefied tissue and solution are aspirated through the lumen 22 andthrough the aspirating tube 36 when the vacuum source 37 is activated ina manner well known in the art, such as through the use of a foot pedal.The aspiration and irrigation take place simultaneously. Furthermore, itshould be noted that the aspiration takes place substantially throughoutthe procedure. That is, it is believed that it is neither necessary nordesirable to liquefy the entire target tissue before aspirating thesame. Rather, as a portion of the target tissue is liquefied by theheated solution, it is irrigated by the cooled solution and aspirated.This process continues until the entire target tissue has been liquefiedand aspirated. In some systems, however, irrigation is not necessary andthe liquefied tissue may be aspirated without irrigation.

The present method applies an energy source to the target tissue inorder to liquefy the same. The present method differs from prior artmethods in that the energy source in the present method is “wet-heat.”That is, it uses the heat transfer modality of convection primarilyrather than the heat transfer modalities of conduction and radiation.

In liquefaction, temperature is more influential than pressure; however,the heated solution must be “in motion” for liquefaction to occur. Thepresent method uses a surgical device, such as a catheter or a handpieceas described above, through which solution is ejected under a minimaldegree of pressure. The solution has to be “in motion” because thetarget tissue is liquefied by the heat transfer principle of convection.In this manner the target tissue, which may be fatty tissue, isliquefied and aspirated.

It should be noted that the concept of liquefaction also refers to“gelifaction” or “gelifying.” That is, the “liquid” may be part liquid,part gel, or part vapor, as long as that liquid is of such a state ofmatter that can be aspirated with low pressure suction/aspirationtechnology. A “solid,” on the other hand, is a state of matter thatcannot be aspirated with the present low pressure suction/aspirationtechnology. Furthermore, aspiration refers to the technology of lowpressure suction/aspiration, such as the procedure used inirrigation/aspiration procedures in cataract extraction. However, thisdoes not eliminate the possibility of using higher pressure aspirationsystems in some selected surgical sites.

The present method may also be used in such areas as prostatectomy,vascular atherectomy/thrombectomy, and tumor removal. Furthermore, thetarget tissue may be subcutaneous fat, atheromatous plaque, or a uterinefibroid. Again, the tip may be any size and shape in order toaccommodate the area of the body being treated. Also, the tip, cannula,and tubes may be replaced in order to re-use the device. Chemicallyactive facilitators may be added to the liquid that is to be heated inorder to achieve additional efficaciousness of liquefaction. Forexample, fibrinolysin and EDTA may be used to liquify a fibrin-rich,calcium-rich atheromatous plaque. Also, a cytotoxic chemical agent maybe added to the liquid in order to remove a tumor.

EXAMPLE

Four pieces of tissue were cut from fresh bovine subcutaneous fatsurrounded by muscle tissue and blood vessels. Each piece wasapproximately two inches by two inches by two inches. Each cube oftissue contained about 95% fat tissue and 5% muscle tissue with someobvious blood vessels present. Two cubes were placed in a control groupand two cubes were placed in an experimental group. The control groupcubes were taken from the refrigerator and placed in a microwave ovenfor two five-second intervals at a high temperature setting. This wasdone in order to raise the temperature of the fat tissue toapproximately human body temperature. The two cubes were placed in atray. A water pik (Teledyne Water Pik, model WP-20W) was set at apressure setting of 5 which equates to 75 psi. The liquid shoots out at20 pulses per second. The bolus size per pulse was 0.27 ml. Roomtemperature tap water was poured into the water pik well. Thetemperature was measured at 80° F. The tip of the water pik was placeddirectly on the first fat cube and the water pik was turned on. Thepulsating water was exposed to the fat cube for approximately oneminute. There was no discernible effect. The same procedure was carriedout on the second fat cube. Again, there was no discernible effect.

The two fat cubes in the experimental group were then subjected to thesame procedure as the control group with the exception that the waterpik well was now filled with 120° F. tap water. Again, the water pik wasturned on with the tip in the same place and was allowed to run forabout one minute. In the first cube there was a tremendous effect. A 95%reduction in the mass of the cube was observed. There was no obviouseffect on either the muscle tissue or on the blood vessel. There was awhitish fat liquid left in the tray. This liquid fat did not re-solidifyand it readily poured out of the tray. The second fat cube was subjectedto the same procedure, with the same result.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof andaccordingly, reference should be made to the appended claims rather thanto the foregoing specification as indicating the scope of the invention.

We claim:
 1. A method for liquefying solid tissue within a bodycomprising the steps of: heating a biocompatible fluid; presenting saidfluid to target tissue within a surgical area so that said target tissueis liquefied when contacted with said heated fluid while leavingnon-target tissue intact; and aspirating said melted target tissue. 2.The method as claimed in claim 1 wherein said fluid is saline.
 3. Themethod as claimed in claim 1 wherein said target tissue is fatty tissue.4. The method as claimed in claim 1 wherein said target tissue issubcutaneous fat.
 5. The method as claimed in claim 1 wherein saidtarget tissue is artheromatous plaque.
 6. The method as claimed in claim1 wherein said target tissue is prostate tissue.
 7. The method asclaimed in claim 1 wherein said target tissue is a tumor.
 8. The methodas claimed in claim 1 wherein said target tissue is a uterine fibroid.9. The method as claimed in claim 1 wherein said heating step includesheating said fluid to a temperature at which temperature only saidtarget tissue melts.
 10. The method as claimed in claim 1 wherein saidfluid is heated to a temperature between 98.6 and 250° F.
 11. The methodas claimed in claim 1 further including the step of adding chemicalsubstances to the heated fluid to facilitate liquefying said targettissue.
 12. The method as claimed in claim 1 further including the stepof irrigating said surgical area while simultaneously aspirating saidmelted target tissue.
 13. The method as claimed in claim 1 furtherincluding the steps of irrigating said surgical area as a portion ofsaid target tissue is liquefied and aspirated and repeating saidpresenting, irrigating, and aspirating steps until the desired amount ofsaid target tissue has been liquefied and aspirated.
 14. A liquefactionapparatus for liquefying solid tissue within a body comprising: a sourceof heated solution; means for directing said heated solution to thetissue in order to liquefy only the tissue; means for irrigating thetissue while the heated solution is being applied to the tissue; andmeans for aspirating the liquefied portion of the tissue.
 15. Theliquefaction apparatus claimed in claim 14 wherein said means forirrigation supply source and said means for aspirating includes a vacuumsource.